Raipur: A massive operation against Naxalites involving about 10,000 security personnel in a hilly region along the Chhattisgarh-Telangana border continued for the fifth day on Friday, a senior official said. It is believed that some 500 cadres of the banned CPI (Maoist) including top leaders are holed up in the area, and Telangana Police are assisting in the exercise, said the official who is monitoring the action on the ground.The operation, one of biggest counter-insurgency actions launched in the Bastar region, involves personnel of different units including the District Reserve Guard, Bastar Fighters and Special Task Force of the Chhattisgarh police, the Central Reserve Police Force and its elite Commando Battalions for Resolute Action (CoBRA).On Thursday, three women Naxalites were killed on Karregutta hills, and a huge cache of weapons, explosives and other materials was recovered. The operation was launched on Monday in the densely forested hills of Karregutta and Durgamgutta along the inter-state border. Parts of the area fall in the Bijapur district of Chhattisgarh, over 450 km away from state capital Raipur.It is believed to be the base of the PLGA (People's Liberation Guerilla Army) battalion No. 1, the strongest military formation of the Maoists, an official said. Intelligence inputs suggest more than 500 Naxalites belonging to PLGA battalion No 1, Telangana state committee and Dandakaranya Special Zonal Committee of Maoists led by senior Maoists such as Hidma and Damodar are holed up in the area, he said."It is a crucial operation because it would be a battle to finish off the military strength of outlawed CPI (Maoists) by targeting PLGA battalion no 1 and the Maoists think tank in Dandakaranya special zonal committee (DKSZC) and Telangana state Committee," the official said.On Thursday, though the bodies of three Naxalites were recovered, many more might have been killed or seriously injured in the gunfight, he said, adding the entire area has been cordoned off."This operation is like a Test cricket match. It would last long and we would not get very exciting news in every session. But at the end of the match, we are hopeful of very favourable result," the official said.All stakeholders of Centre, Chhattisgarh government and neighboring states are directly or indirectly involved in this operation, he said. "So far, all our troops are safe. No problems except for the hardship of tough terrain and hot summer. But the morale of the troops is high," he said.Helicopters and drones are being used in the operation, the official added. As per sources, some jawans involved in the operation were shifted to hospital after they suffered dehydration and heatstroke.The security forces have killed more than 350 Naxalites in a string of encounters, mostly centred in the Bastar region, since January last year. As many as 18 Naxalites, including 11 women, were killed in twin encounters in Bastar region on March 29.So far this year, 144 Naxalites have been gunned down in separate encounters in the state. Of these, 128 were eliminated in the Bastar division comprising seven districts, including Bijapur.